The use of ultrasonic medical devices in surgery is widely known in various surgical fields. Traditional surgical instruments using ultrasonic frequencies typically use the ultrasonic energy to dissect, coagulate, and cut living tissue during surgery. Existing ultrasonic surgical devices typically employ an ultrasonic transducer to translate electrical energy provided to the transducer into mechanical energy for use in the intended surgical procedure. The mechanical vibratory motion is typically delivered to a distal end of the surgical instrument where a cutter is located. Due to the mechanical vibratory motion, heat is generated at the cutter. In traditional medical procedures this heat is a sought after byproduct of the ultrasonic mechanical energy delivered to the cutter, as the heat aids in the coagulation of tissue that is cut by the surgical instrument.
The heated output of traditional ultrasonic surgical devices, however, does introduce several inherent problems when used in various forms of surgery. If these devices are used to attempt to cut bone, for example, the high concentrated heat and mechanical vibration can result in the temporary or permanent loss of blood supply to the region of bone in contact with the surgical device. This loss of blood supply in the bone is associated with necrosis of the bone, wherein bone tissue dies. Such death of bone tissue is not clinically desirable. In light of this, the use of ultrasonic cutting techniques with dense materials such as bone is not practical and is generally avoided. When faced with a need to cut bone, traditional invasive procedures are generally used. These invasive procedures generally require a larger incision and expose a patient to a greater risk of injury or infection. Furthermore, traditional mechanical means used to cut bone often employ vibrating or rotating instruments. Such instruments may not differentiate between bone and surrounding soft tissue, therefore the potential remains for unintentional damage to the surrounding soft tissue which may result in permanent injury to a patient.
Furthermore, existing bone cutting surgical devices use a combination of low frequency, located outside of the ultrasonic range, and low amplitude levels to slowly cut through bone. With such an approach, however a long period of time is required to cut through a region of bone. During a surgical procedure where the patient is under the effects of aesthesia, a surgeon generally wishes to minimize the time that the procedure takes to perform. While increasing the frequency or amplitude of a bone cutting device would decrease the time required to cut through the bone, such an increase of frequency or amplitude results in excessive heat generation at the cutter and the problems discussed above. Additionally, the high heat of the device results in cauterization of soft tissue which may result in irreversible damage to a patient.